Peng, I'm not trying to be a smart a..., but...
Um, how about a UPS? Weird thought I know, but I wouldn't be without one on my entire network stack, including the asterisk box. If budget allows for it - I'd use a nice full-time inverter unit like a Powerware 9xxx.
Nevertheless, your question is worthwhile, and the answer will be great when you figure it out!
Good luck. /M --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
